📊 See this on a psychrometric chart
Want to plot two state points and visualize the process line — sensible cooling, mixing, dehumidification? Use the visual chart tool. Same psychrometric math; saturation curve, RH grid, and process line drawn. No signup required.
This psychrometric calculator returns the full moist-air state from just two known conditions: dry-bulb temperature plus relative humidity, wet bulb, or dew point. It reports humidity ratio (in lb/lb and grains per pound), enthalpy, specific volume, relative humidity, wet bulb, dew point, water-vapor pressure, and the barometric pressure used — everything you would otherwise read off a psychrometric chart.
Engineers use these properties to size cooling and heating coils, estimate latent versus sensible loads, check condensation risk, and design dehumidification and economizer sequences. Because the tool derives barometric pressure from your elevation, the results stay accurate at altitude where sea-level psychrometrics would over-predict density.
| Saturation pressure | Pws via Magnus / Buck form of T (°F → °C) |
| Humidity ratio | W = 0.62198 · Pw ÷ (P − Pw) |
| Enthalpy | h = 0.240 · T + W · (1061 + 0.444 · T) |
| Specific volume | v = 0.3704 · (T + 460) · (1 + 1.6078 · W) ÷ P |
| Wet bulb | Sprung psychrometer relation, solved for Twb |
The relations follow ASHRAE Fundamentals Chapter 1 (psychrometrics). Saturation vapor pressure Pws uses a Magnus-type (Buck) equation; vapor pressure is Pw = RH · Pws; humidity ratio, enthalpy, and specific volume follow the standard moist-air formulas above. Barometric pressure P is computed from elevation using the standard atmosphere (14.696 psia at sea level), so density-dependent outputs are altitude-corrected. Dew point is found by inverting the saturation curve, and wet bulb by solving the Sprung relation numerically.